With the foreward pistol grip and no stock - I'm thinking the gun could be classified as an AOW, and could be done for the $5 tax stamp as long as it was built by a licensed class III manufacturer and then transfered to the purchaser..........

If a handgun is over 26 inches long, without a butstock and even if the barrel is less than 16 inches, it can have a forward pistol grip. This won't really work on an AK but if the receiver was longer and total length was over 26 inches the barrel can be less than 16 inches. The Thomson pistols did it with a 13 or 13.5 inch barrel adding that to the receiver made 26 inches and the original Tommy guns had 10 inch barrels , so the special length barrels were just to add the pistol grip but the barrel was too short for a buttstock to be a rifle.